RT Book, Section
A1 Bianchi, Diana W.
A1 Crombleholme, Timothy M.
A1 D'Alton, Mary E.
A1 Malone, Fergal D.
SR Print(0)
ID 1106401937
T1 Trisomy 21 (Down Syndrome)
T2 Fetology: Diagnosis and Management of the Fetal Patient, 2e
YR 2015
FD 2015
PB McGraw-Hill Education
PP New York, NY
SN 978-0-07-144201-5
LK obgyn.mhmedical.com/content.aspx?aid=1106401937
RD 2023/12/07
AB Key  PointsNinety  percent  of  individuals  with  Down  syndrome  have  three  full  copies  of  chromosome  21.  Three  to  4%  have  an  unbalanced  translocation,  and  1%  have  mosaicism.Prevalence  in  the  United  States  is  13.65  per  10,000  livebirths.Fetuses  with  Down  syndrome  are  more  likely  to  die  in  utero  than  normal  fetuses.Karyotype  analysis  is  diagnostic.Once  trisomy  21  is  diagnosed,  prospective  parents  should  be  offered  an  echocardiogram  and  a  detailed  sonographic  evaluation  of  fetal  anatomy  (if  not  performed  previously).  Fifty  percent  of  fetuses  have  cardiac  anomalies.If  no  structural  heart  disease  or  gastrointestinal  obstruction  is  present,  delivery  can  occur  in  the  community.  If  structural  anomalies  in  the  heart  or  other  organs  are  present,  delivery  should  occur  in  a  tertiary  center.Newborns  often  have  feeding  difficulties  due  to  hypotonia.There  is  an  increased  risk  of  hematologic  disorders  and  hypothyroidism.Affected  children  have  mild  to  moderate  mental  retardation  (IQ  40—70).The  precise  number  and  function  of  genes  of  21q  is  not  fully  known.Recurrence  risk  for  full  trisomy  21  is  1%,  or  the  maternal  age-associated  risk  (whichever  is  greater).